This invention relates to the use of telecine apparatus for controlling the exposure of cinematographic, i.e. motion picture, films.
The shooting and developing of cinematographic film is a highly artistic process, with many adjustments being made during production in order to result in an end product of optimal quality. One of the aspects that requires control is the exposure of the film.
The variables that contribute to the lightness or darkness of exposed processed film include the following:
The exposure speed of the film stock; PA1 The age and storage conditions of the film stock; PA1 The aperture selected on the film camera; PA1 The lighting conditions and/or weather, depending on whether the film is being shot indoors or outdoors; PA1 The condition of the film processing bath; and PA1 The time spent in the processing bath. PA1 a) using the telecine machine to generate video images from the negative cinematographic film; PA1 b) generating timecode data identifying frames of the negative cinematographic film; PA1 c) generating image adjustment control data to adjust image parameters of the video images generated by the telecine machine, so as to produce video images of a desired quality; PA1 d) using the image adjustment control data to generate exposure level information for frames of the negative cinematographic film; PA1 e) logging in a film exposure logging system timecode data and exposure level information for frames of the negative cinematographic film; PA1 f) using the exposure level information to generate exposure compensation printing settings; PA1 g) printing the positive cinematographic film from the negative cinematographic film, by a printing process in which light is passed through the negative cinematographic film to the unexposed positive cinematographic film; and PA1 h) using the exposure compensation printing settings during the printing process to provide compensation for sub-optimal exposure levels of frames in the negative cinematographic film. PA1 a) using a telecine machine to generate video images from the cinematographic film; PA1 b) generating timecode data for frames of the cinematographic film; PA1 c) generating image adjustment control data to adjust image parameters of the video images generated by the telecine machine so as to produce video images of a desired quality; PA1 d) using the image adjustment control data to generate exposure level information for frames of the cinematographic film; and PA1 e) logging in a film exposure logging system timecode data and exposure level information for frames of the cinematographic film so as to provide the exposure log.
Typically, film shot one day is processed overnight and viewed first thing in the morning. The results of this viewing usually generate data for the fine tuning of the exposure of the film for that day. Traditionally, the exposed film is viewed by projection through a cinema projector onto a screen.
Once a film has been completed, it may be converted into a video format for distribution on, e.g., video tapes or discs or for broadcast. It is usual to convert the film material into electrical signals using a telecine machine. Such a machine consists of a film transport, together with an optoelectric mechanism for sampling the requisite number of lines to make a television picture. Examples of such machines include the URSA Gold machine, manufactured by Cintel International Limited (formerly Rank Cintel Ltd) in Ware, England, and the FDL90 machine, manufactured by BTS in Darmstadt, Germany.
Telecine machines are designed to accept a very wide range of quality of film material, from extremely underexposed to extremely overexposed. Compensation for poor exposure is accomplished by electrical signal processing within the electronics of the telecine machine. Further signal processing equipment that can affect the visual attributes of the picture include devices referred to as secondary colour correctors. Whilst it is the primary function of such devices to alter certain colour attributes, they can also affect the overall signal level. One such example of a secondary colour corrector is the DCP manufactured by Pandora International Ltd. in Kent, England. In practice, such a device would be controlled in use by a Pandora POGLE controller also manufactured by Pandora International Ltd. The electrical signal processing can be accomplished either in the analogue domain, via analogue `characteristic` changing, with capacitive and inductive components, or preferably with digital lookup tables. These tables are one dimensional, and the input value is used as the address at which to look up the data that is used as the output value. This is standard technique in the design of digital electronic circuitry. In practice, all professional telecine control is accomplished from programmer/controller devices such as the Pandora POGLE or the Da Vinci RENAISSANCE. Such control signals may include, but are not limited to: Master Gain; Master Lift; Master Gamma; Differential Gain; Differential Lift; Differential Gamma; and Secondary corrections of each of the Red, Green or Blue content of the Red, Green, Blue, Cyan, Magenta and Yellow. The control settings in both of the above devices are digital parameters, which are usually not interrogated by the operator, but are internally stored in conjunction with either a scene number or a timecode reference. This allows scene-by-scene programming.
Whilst the use of such equipment results in a satisfactory end product in video format, it has no effect on the quality of the original cinematographic film, and any problems with exposure will remain.
In U.S. Pat. No. 5,276,522 of Terence W. Mead there is proposed a telecine machine in which the original film is scanned, corrections and editing is carried out on the scanned images, and then a second cinematographic film is produced by using a cathode ray tube as a writer to expose the film. The resultant film will be of inferior quality to film produced in a conventional optical manner using a camera or printing a positive from a negative. Although the film produced by Mead may include colour correction and other editing decisions, there are significant disadvantages as compared to the production of film by conventional optical means.
During the production of a cinematographic film it is known to view the film in a video format on a television type monitor. This is desired for a number of reasons. One reason is that it is common to shoot negative material, which is analogous to the negatives that one receives with prints shot in a stills camera. To view negative material, it is necessary to print it onto positive material prior to viewing it. Thus this is an expensive and time consuming extra process, and also a stage adding another degree of variation. Another reason for wanting to view the film in video format on a monitor is that the material may be expressly intended for television distribution, and therefore this may the best way to judge its quality and content for that purpose. To view the film in a television or video format, it is possible to use a telecine machine. However, a problem is that it is possible to produce evenly balanced television images from film that is significantly under or over exposed, that being a feature of conventional telecine machines. In such cases there is no indication to the film shooting crew that the exposure is incorrect. In any event, even if it is noticed that there is serious under or over exposure, there is still the problem of how to deal with this on the film that has actually been shot if it is wished to keep that take.